What is litmus paper made of?

Written by neal litherland

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Litmus paper, used in chemistry classes in schools the world over, is used to determine the acidic content of a substance, also called pH. The name of this paper is commonly used to describe a test where a single factor determines the outcome, labelling it a litmus test. Many people may wonder though, just what this chemically treated testing paper is made of.

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Paper

Litmus paper is primarily made out of paper. The paper is mostly made up of wood cellulose, which is treated with solvents beforehand to make sure there are no contaminants.

Lichens

Litmus paper is infused with lichens. Lichens are considered to be both an algae and a fungus, and they're quite sensitive to environmental change, which gives litmus paper its colour changing ability.

Specifics

The two most common lichens found in litmus paper are rocella tinctoria and lecanora tartarea.

Design

Litmus paper comes in two colours, red and blue. The natural colour is blue, and when it comes into contact with an acid the paper turns red. When the process is reversed, and the red paper comes into contact with a base, it returns to the natural blue colour.

Manufacturing

During the manufacturing process wood pulp is converted to paper, purified, then lichens are added, and the paper is allowed to dry and is packaged.